Questions about forced Germanization of Poles in WWII

I only have two confirmed Germanization stories in my family, but I still have tons of questions and confusion surrounding everything on it. If someone is an expert in even the slightest on this topic, any insight would be greatly appreciated:)

The father of my great-Babcia, Franciszek Klimecki, and his second wife Maria Marcinkowska were presumably forced to become German when the Nazis took them. The details are sort of blurry, but I know they ended up in East Germany, specifically Greifswald, Specifcally Kolzin Ausbau:)

I know their names were changed to Franz Klimetzki and Marie Klimetzki, and were taught German. They were in contact with my great-Babcia back in America, and when they wrote out her name they wrote it as ,Marie Klimetzki'- guess how happy that made me:/. The weird thing is- for their address it wasn't a house, rather their post office. Is there any reason for that? Why wouldn't they just put their house number? And why would they Germanize his daughter's name?

But at the same time, the way they spelt her name changed between years. Sometimes they called her Marie Klimetzki, sometimes Maria Klimecka, and when she got married they sometimes put her married Polish name with the proper ,Ska' on the end. Sometimes they didn't and put the ,Ski' at the end. It doesn't make sense.. is this just a mystery that only they could answer, or is there a reason for this? I keep thinking that this is maybe the years the DDR loosened up, I heard of a woman whose envelopes and photos sent to her father were kept by the government, that maybe they judged which letters got sent based on the recipient?

Were Poles normally under the radar in their Germanized homes? I contacted the Greifswald Archives, and they told me they had nothing for him. I can't imagine, Franciszek and Maria lived there for atleast 20 years and had no documentation? Also, were a lot of Poles sent to East Germany? Is there a reason for that?

I really thank anyone who took the time to read my ramblings and if you answer I thank you a million times more.

And finally, is there anyway to find out what happened to them? What happened to all their belongings once they died? He must've had photos and extremely valuable things (at least to me).. where did they all go?